Photovoltaic system and control method

Abstract

Provided are a photovoltaic system and a control method. The system comprises: a conversion circuit, a power taking circuit, a trip switch, a switching power supply and a controller. The trip switch is connected between the conversion circuit and an input end of a converter. The power taking circuit is configured to take power from at least one photovoltaic module string and supply power to the switching power supply. The switching power supply is configured to supply power to the controller and the trip switch when the power taking circuit provides power normally. The controller is configured to, when a photovoltaic module string has a fault, at least disconnect the trip switch corresponding to the fault photovoltaic module string, to disconnect connection between the faulty photovoltaic string and the conversion circuit.

1 . A photovoltaic system, comprising a conversion circuit, a power taking circuit, a trip switch, a switching power supply and a controller, wherein
 the trip switch is connected between the at least two photovoltaic module strings conversion circuit and an input end of a converter;   the power taking circuit is configured to take power from at least one photovoltaic module string and supply power to the switching power supply;   the switching power supply is configured to supply power to the controller and the trip switch when the power taking circuit provides power normally; and   the controller is configured to, when a photovoltaic module string has a fault, at least disconnect the trip switch corresponding to the fault photovoltaic module string, to disconnect connection between the faulty photovoltaic string and the conversion circuit.   
     
     
         2 . The photovoltaic system according to  claim 1 , wherein the power taking circuit comprises a positive power taking circuit and a negative power taking circuit; and
 the positive power taking circuit is connected to a positive electrode of the at least one photovoltaic module string, and the negative power taking circuit is connected to a negative electrode of the at least one photovoltaic module string.   
     
     
         3 . The photovoltaic system according to  claim 1 , further comprising a bidirectional rectifier circuit, wherein
 the bidirectional rectifier circuit is connected between the power taking circuit and the switching power supply; and   the bidirectional rectifier circuit is configured to rectify an output voltage and an output current of the power taking circuit and provide a rectified output voltage and a rectified output current to the switching power supply.   
     
     
         4 . The photovoltaic system according to  claim 3 , wherein
 the bidirectional rectifier circuit comprises a first diode, a second diode, a third diode and a fourth diode;   a cathode of the first diode and a cathode of the second diode are connected to a positive end of the switching power supply, and an anode of the second diode and an anode of the first diode are respectively connected to the positive power taking circuit and the negative power taking circuit; and   a cathode of the third diode and a cathode of the fourth diode are respectively connected to the anode of the first diode and the anode of the second diode, and an anode of the third diode and an anode of the fourth diode are connected to a negative end of the switching power supply.   
     
     
         5 . The photovoltaic system according to  claim 1 , further comprising: a fifth diode and a sixth diode;
 wherein the conversion circuit comprises a DC-DC conversion circuit, the DC-DC conversion circuit is connected between the trip switch and the switching power supply, a positive end of the DC-DC conversion circuit is connected to a positive end of the switching power supply through the fifth diode, and a negative end of the DC-DC conversion circuit is connected to a negative end of the switching power supply through the sixth diode.   
     
     
         6 . The photovoltaic system according to  claim 5 , wherein when the at least two photovoltaic module strings are connected correctly, the one with higher voltage of the power taking circuit and the DC-DC conversion circuit supplies power to the switching power supply. 
     
     
         7 . The photovoltaic system according to  claim 1 , wherein the power taking circuit further comprises a maintenance switch and a bidirectional rectifier circuit, and the bidirectional rectifier circuit is connected between the power taking circuit and the switching power supply, wherein
 the maintenance switch is connected between the at least two photovoltaic module strings and the bidirectional rectifier circuit, or the maintenance switch is connected between the bidirectional rectifier circuit and the switching power supply; and   when the trip switch is to be closed, the maintenance switch is first closed if the maintenance switch is disconnected and then the trip switch is closed.   
     
     
         8 . The photovoltaic system according to  claim 5 , further comprising: a seventh diode and an eighth diode;
 wherein the seventh diode is connected between a positive end of the maintenance switch and a positive input end of the bidirectional rectifier circuit, and the eighth diode is connected between a negative end of the maintenance switch and a negative input end of the bidirectional rectifier circuit.   
     
     
         9 . The photovoltaic system according to  claim 1 , wherein both the controller and the switching power supply are provided inside a cabinet where the conversion circuit is housed. 
     
     
         10 . A photovoltaic system, comprising at least two sets of trip switches as follows: a first trip switch and a second trip switch, each of the at least two sets of trip switches comprises a plurality of contacts, and each contact is connected to a corresponding photovoltaic module string;
 the first trip switch is connected to positive electrodes of all photovoltaic module strings and negative electrodes of a subset of the photovoltaic module strings, and the second trip switch is connected to negative electrodes of a remaining photovoltaic module string,   or,   the first trip switch is connected to negative electrodes of all photovoltaic module strings and positive electrodes of a subset of the photovoltaic module strings, and the second trip switch is connected to the positive electrodes of a remaining photovoltaic module string.   
     
     
         11 . A photovoltaic system, comprising: a switching power supply, a conversion circuit and a trip switch, wherein
 the trip switch comprises a plurality of contacts, and each of the contacts is connected to a corresponding photovoltaic module string;   a first end of the conversion circuit is connected to the photovoltaic module strings through the trip switch, and a second end of the conversion circuit is connected to the switching power supply; and   the trip switch is connected to one of the photovoltaic module strings, and the trip switch is then connected to the other photovoltaic module strings if the switching power supply works   normally, and the trip switch is not connected to the other photovoltaic module strings corresponding to the trip switch if the switching power supply does not work.   
     
     
         12 . A control method of a photovoltaic system, wherein the photovoltaic system is a photovoltaic system according to  claim 1 ; and
 wherein the method comprises:   supplying power, by the switching power supply, to the trip switch when the power taking circuit provides power normally;   closing the trip switch; and   controlling the trip switch to be disconnected when there is a wiring fault in the photovoltaic module string.   
     
     
         13 . The control method according to  claim 12 , wherein the photovoltaic system further comprises a maintenance switch connected between the power taking circuit and the switching power supply; and
 wherein the method further comprises:   closing the maintenance switch before closing the trip switch.   
     
     
         14 . The control method according to  claim 12 , wherein the photovoltaic system further comprises a DC-DC conversion circuit and a DC-AC conversion circuit;
 wherein an input end of the DC-DC conversion circuit is connected to the trip switch, and an output end of the DC-DC conversion circuit is connected to the DC-AC conversion circuit; and   wherein the method further comprises:   disconnecting the maintenance switch when the DC-AC conversion circuit fails.   
     
     
         15 . A control method of a photovoltaic system, wherein the photovoltaic system is a photovoltaic system according to  claim 10 ; and
 wherein the method comprises:   controlling the first trip switch to connect to positive electrodes of all photovoltaic module strings and negative electrodes of a subset of the photovoltaic module strings, and controlling the second trip switch to connect to negative electrodes of a remaining photovoltaic string;   or,   controlling the first trip switch to connect to negative electrodes of all photovoltaic module strings and positive electrodes of a subset of the photovoltaic module strings, and controlling the second trip switch to connect to the positive electrodes of a remaining photovoltaic module string.   
     
     
         16 . A control method of a photovoltaic system, wherein the photovoltaic system is a photovoltaic system according to  claim 11 ; and
 wherein the method comprises:   connecting the trip switch to one of the photovoltaic module strings; and   connecting the trip switch to the other photovoltaic module strings if it is determined that the switching power supply works normally, and not connecting the trip switch to the other photovoltaic module strings if it is determined that the switching power supply does not work.   
     
     
         17 . The photovoltaic system according to  claim 1 , wherein the controller is further configured to disconnect the trip switch corresponding to the faulty photovoltaic string when the photovoltaic string has a fault. 
     
     
         18 . The photovoltaic system according to  claim 1 , wherein a positive power taking circuit, and the positive power taking circuit is connected to a positive electrode of the at least one photovoltaic module string. 
     
     
         19 . The photovoltaic system according to  claim 1 , wherein a negative power taking circuit, and the negative power taking circuit is connected to a negative electrode of the at least one photovoltaic module string. 
     
     
         20 . The photovoltaic system according to  claim 1 , wherein
 the power taking circuit further comprises a maintenance switch connected between the power taking circuit and the switching power supply; and   when the trip switch is to be closed, the maintenance switch is first closed and then the trip switch is closed.